For ultra-long-haul optical fiber communication system, the traditional communication mode is to set up a relay station in the line, in which the optical signal is amplified and shaped before transmission. However, the transmission line route of the industry private network, especially the power system, is usually remote, passing through harsh areas such as desert and mountain range, it is difficult to find a suitable optical relay station. In addition, the construction of independent optical relay station along the line also needs to build new infrastructure (including civil engineering, electrical engineering, fire protection, HVAC, etc.), which will be affected by many factors such as site selection, land acquisition, external power supply, construction conditions, etc. during the construction, and after put into operation, any failure in the power environment of the machine room, external power supply, incoming optical cable, optical transmission equipment and others will also affect the reliability of communication circuit. The ultra-long haul optical transmission technology has the characteristics of end-to-end direct access, no relay equipment, low operation and maintenance cost and so on. The optical subsystem products of Accelink use ultra-long-haul optical transmission technology to effectively realize long-distance direct communication, reduce the relay station faults, and improve the stability and safety of line operation.